Many industrial applications of materials require the surfaces of these products to possess hydrophobic and oleophobic character for both aesthetic as well as practical reasons. Coated glass cloth, employed in pre-fabricated air-supported structures such as sports stadia, for example, should have an oil repellent surface so as to prevent unsightly dirt accumulation. High voltage electrical insulators, likewise, must be hydrophobic and "self-cleaning" in contaminated environments such that surface dirt and moisture, and therefore undesirable arc tracking, are kept to a minimum. Furthermore, many coatings, such as those applied to optics, mirrors, windshields, solar collectors, and greenhouses, must retain clarity to be efficient light transmitters, and therefore also have to be "self-cleaning" (e.g., as by rainfall) relative to the uncoated surfaces. Finally, as yet another illustration of the utility of low surface energy coatings, the treatment of various fabrics for water repellency and stain resistance (i.e., oleophobicity) has become a major commercial success.
It is known in the coating arts to employ silicones to achieve hydrophobic surfaces and treated fabrics. Likewise, perfluorinated organic coatings and fabric treatments are known to confer oleophobic properties. Indeed, these two classes of materials have been effectively combined in U.S. Pat. No. 4,410,563 to coat optical glass surfaces as well as in U.S. Pat. No. 3,681,266 to treat fabrics.
Unfortunately, the perfluorinated organic compounds are quite costly and therefore not suitable for many applications in which oleophobic surfaces would otherwise prove desirable. Such disadvantage was partially overcome by U.S. Pat. No. 3,317,629, wherein fluoroalkylsiloxanes were "extended" with acrylic polymers and used to treat a variety of fabrics to obtain hydrophobic and oleophobic character. In a similar fashion, U.S. Pat. No. 4,070,152 employs a copolymer of a maleic-anhydride copolymer, a fatty acid amine and an aminoorganopolysiloxane as an extender for fluorinated "textile treating resins." It discloses improved oil and water repellency and better retention of repellency after laundering and dry cleaning relative to use of the textile treating resins alone. Still further examples of this general concept are provided by Japanese Pat. Nos. 142,958/83 and 147,483/83 which combine a perfluoroalkyl-containing silane and a silane coupling agent with water-glass and colloidal silica, respectively, for use as a water and oil repellent agent for glass surfaces.
Although such attempts to reduce the expense of fluorinated treating resins have been successful in that less of the costly ingredient is required to achieve the same extent of surface modification, complex and costly reaction schemes are sometimes required to produce the disclosed components. Furthermore, it is known from Jarvis et al. (Contact Angle, Wettability, and Adhesion, p. 317, American Chemical Society, Washington, D.C., 1964) that only certain combinations of fluorinated organic compounds and (extending) polymers result in low energy surfaces. Moreover, this reference teaches that a critical balance of organophilic/organophobic character (i.e., the precise solubility/insolubility balance of the fluorinated compound in the polymer) is required of the modifying fluorinated compound if the modified polymer combination is to produce a uniform, clear, high quality film, in addition to low surface energy. It is therefore recognized in the art that there is no a priori way to determine how much of, and indeed, which of the many available fluorinated organic compounds, or other low surface energy modifiers, can be successfully combined with a given polymer to produce the desired hydrophobic/oleophobic character while maintaining a uniform, high quality surface.